Filling material, resin composition, package, and light-emitting device

ABSTRACT

A filling material for a resin composition includes a base material and a coating material coating at least a portion of a surface of a particle of the base material. The base material comprises a first inorganic compound containing a Group II element. The coating material comprises a second inorganic compound containing the Group II element and is different from the first inorganic compound. A method of manufacturing the filling material is provided. A resin composition comprising the filling material, a package, a light-emitting device, and methods of manufacturing them are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of the U.S. patent application Ser. No.15/852,823 filed on Dec. 22, 2017, which claims priority under 35 U.S.C.§ 119 to Japanese Patent Application No. 2016-250608, filed on Dec. 26,2016, the contents of which are hereby incorporated by reference intheir entirety

BACKGROUND 1. Field of the Invention

The present disclosure relates to a filling material, a resincomposition, a package, and a light-emitting device.

2. Description of Related Art

Resin compositions containing light-reflecting substances are widelyused for packages of light-emitting devices. With recent reduction inthe size and thickness of light-emitting devices, improvement of themechanical strength of resin compositions has been demanded. Forexample, Japanese Patent Publication No. 2002-294070 proposes a resincomposition intended to have an improved mechanical strength by adding afibrous filling material composed of wollastonite.

The above-mentioned wollastonite is obtained by milling a silicatemineral, which is a natural mineral, into a fibrous form and is used asa filling material for the resin composition. Accordingly, while miningthe silicate mineral, mineral magnetite (Fe₃O₄) may also be mined andincorporated as an unavoidable impurity. In addition, tools used formining and milling the silicate mineral may wear away, resulting in ironbeing incorporated as an unavoidable impurity. Once the iron andmagnetite (hereinafter referred to as “iron component”) is incorporatedinto the silicate mineral, it is difficult to remove them to obtain apure wollastonite. If, for example, a resin composition containing thewollastonite containing those unavoidable impurities is used in apackage of a light-emitting device, light emitted from a light-emittingelement is likely to be absorbed in the iron component contained in thewollastonite, resulting in decreased light reflection of the package.This may lead to decreased light-extraction efficiency of thelight-emitting device.

In view of the foregoing, Japanese Patent Publication No. 2015-5675(hereinafter referred to as Patent Literature 2) proposes coating thesurface of fibrous particles composed of wollastonite with alight-reflecting material and using the coated particles as a fillingmaterial. This proposal is directed to improvement in both themechanical strength and the light reflectivity of the resin composition.

SUMMARY

According to an embodiment of the present disclosure, a filling materialincludes a base material and a coating material coating at least aportion of a surface of a particle of the base material. The basematerial comprises a first inorganic compound containing a Group IIelement. The coating material comprises a second inorganic compoundcontaining the Group II element and is different from the firstinorganic compound.

According to an embodiment of the present disclosure, a resincomposition includes a light transmissive resin and the filling materialdispersed in the resin. The resin has a refractive index lower than thatof the base material and higher than that of the coating material.

Preferably, the base material has a refractive index of 1.60 to 1.80;the resin has a refractive index of 1.48 to 1.59; and the coatingmaterial has a refractive index of 1.35 to 1.47.

According to an embodiment of the present disclosure, a package has arecess for mounting a light-emitting element, wherein the recess has aninner surface having at least a portion comprising the resincomposition.

According to an embodiment of the present disclosure, a light-emittingdevice includes the package and a light-emitting element mounted in therecess.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of embodiments of the invention and many ofthe attendant advantages thereof will be readily obtained by referenceto the detailed description below when considered in connection with theaccompanying drawings.

FIG. 1 is a perspective view showing a light-emitting device accordingto an embodiment of the present disclosure.

FIG. 2A is a cross-sectional view taken along line IIA-IIA in FIG. 1.

FIG. 2B is a schematic diagram of a resin composition according to theembodiment, partially enlarging region IIB shown in FIG. 2A.

FIG. 3 is a flowchart for a method of manufacturing a light-emittingdevice according an embodiment of the present disclosure.

FIG. 4A is a schematic cross-sectional view illustrating a particle of afirst inorganic compound, which is an original material of a firstfilling material, in a method of manufacturing a light-emitting deviceaccording to an embodiment of the present disclosure.

FIG. 4B is a schematic cross-sectional view illustrating a particle of afirst inorganic compound after being subjected to a surface treatmentstep in a method of manufacturing a light-emitting device according toan embodiment of the present disclosure.

FIG. 4C is a schematic cross-sectional view illustrating a particle of afirst inorganic compound after being subjected to a heat treatment stepin a method of manufacturing a light-emitting device according to anembodiment of the present disclosure.

FIG. 4D is a schematic cross-sectional view illustrating anotherparticle of a first inorganic compound after being subjected to a heattreatment step in a method of manufacturing a light-emitting deviceaccording to an embodiment of the present disclosure.

FIG. 5A is a photograph of a first filling material before beingsubjected to the surface treatment in an example of the presentdisclosure.

FIG. 5B is a photograph enlarging a part of the first filling materialshown in FIG. 5A.

FIG. 6A is a photograph showing a first filling material that has beensubjected to the surface treatment in the example.

FIG. 6B is a photograph enlarging a part of the first filling materialshown in FIG. 6A.

FIG. 7A is a photograph showing a first filling material that has beensubjected to the heat treatment at a temperature of 850° C. in anexample of the present disclosure.

FIG. 7B is a photograph enlarging a part of the first filling materialshown in FIG. 7A.

FIG. 8A is a photograph showing a first filling material that has beensubjected to the heat treatment at a temperature of 900° C. in anexample of the present disclosure.

FIG. 8B is a photograph enlarging a part of the first filling materialshown in FIG. 8A.

FIG. 9A is a photograph showing a first filling material that has beensubjected to the heat treatment at a temperature of 950° C. in anexample of the present disclosure.

FIG. 9B is a photograph enlarging a part of the first filling materialshown in FIG. 9A.

FIG. 10A is a photograph showing a first filling material that has beensubjected to the heat treatment at a temperature of 970° C. in anexample of the present disclosure.

FIG. 10B is a photograph enlarging a part of the first filling materialshown in FIG. 10A.

FIG. 11A is a photograph showing a first filling material that has beensubjected to the heat treatment at a temperature of 1000° C. in anexample of the present disclosure.

FIG. 11B is a photograph enlarging a part of the first filling materialshown in FIG. 11A.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a description is given of a light-emitting device accordingto an embodiment of the present disclosure.

The drawings referenced in the following description schematically showthe embodiment. Thus, the scale of members, distances between members,positional relations between members or the like may be presented in anexaggerated manner, and illustration of a part of a member may beomitted. Furthermore, the scale and distances between members may notmatch between a perspective view and its corresponding cross-sectionalview. In the description below, members that are the same or analogousare given the same name or number in principle, and duplicative detaileddescriptions are appropriately omitted.

It is to be noted that, in a light-emitting device and a method ofmanufacturing the device according to the embodiment, interpretation ofdirections like “up”, “down”, “left”, and “right” should be interchangedaccording to the situation. It is to be noted that, directions like “up”and “down” are used to represent relative positions between constituentelements in a drawing referenced for explanation and are not intended tospecify the absolute positions unless otherwise stated.

A particle diameter is, unless otherwise stated, indicated by an averageparticle diameter determined as a Fisher Sub Sieve Sizer's No.(F.S.S.S.No.) using an air permeation method. Specifically, under anenvironment of a temperature of 25° C. and a humidity of 70%, 1 cm³ of asample is measured and packed in a special tubular vessel and then a dryair is passed through the vessel at a constant pressure. The specificsurface area is obtained based on the difference in the pressure andconverted to the average particle diameter.

Embodiment

Configuration of Light-Emitting Device

A description is given of the configuration of a light-emitting deviceaccording to an embodiment with reference to FIGS. 1 to 2B. FIG. 1 is aperspective view illustrating the configuration of the light-emittingdevice according to the embodiment. FIG. 2A is a cross-sectional viewtaken along line IIA-IIA of FIG. 1, illustrating the configuration ofthe light-emitting device according to the embodiment. FIG. 2B is aschematic diagram illustrating a enlarged view of region IIB of aresin-molded body in the light-emitting device shown in FIG. 2A.

In FIGS. 1 and 2A, XYZ-axis coordinates are indicated for the sake ofillustration. The X-axis is in a longitudinal direction of thelight-emitting device 1 having an elongated, substantially rectangularparallelepiped shape; the Y axis is in a lateral direction of thelight-emitting device 1; and the Z-axis is in a thickness direction ofthe light-emitting device 1.

The light-emitting device 1 according to the embodiment includes apackage 2 having a recess 2 a, a light-emitting element 3 mounted on abottom surface 2 b of the recess 2 a, and a light-transmissive sealingmember 4 disposed in the recess 2 a to seal the light-emitting element3. The package 2 includes a pair of lead electrodes 21 and aresin-molded body 22 holding the pair of lead electrodes 21.

The external shape of the light-emitting device 1 is an elongated,substantially rectangular parallelepiped shape and has a thin thickness,which corresponds to the dimension of the light-emitting device 1 in theZ-axis direction. The light-emitting device 1 has an end surface locatedfurthest in the negative Z-axis direction and serving as a mountingsurface. The recess 2 a of the light-emitting device 1 is formed such asto have an opening at an end side of the light-emitting device 1 locatedfurthest in the negative Y-axis direction. Thus, the light-emittingdevice 1 is suitable to the side-view mounting in which thelight-emitting device 1 emits light in a direction parallel to themounting surface.

In the light-emitting device 1 according to the embodiment, theresin-molded body 22 of the package 2 is formed using a resincomposition 20 containing a resin 201 containing a first fillingmaterial 202 for improving the mechanical strength of the resin 201. Thefirst filling material 202 may contain a fibrous base material 202 a anda coating material 202 b coated on the surface of the base material 202a to enhance light reflectivity. The resin composition 20 may furthercontain a second filling material 203 for enhancing light reflectivityor other filling materials.

Package

The package 2 includes the pair of lead electrodes 21 and theresin-molded body 22 that holds the pair of lead electrodes 21 such thatthe pair of lead electrodes are spaced apart from each other. In thepresent embodiment, the opening of the recess 2 a of the package 2 openslaterally in a direction parallel to the end surface located furthest inthe negative Z-axis direction and serving as the mounting surface. Thebottom surface 2 b of the recess 2 a is formed substantiallyperpendicular to the mounting surface.

The bottom surface 2 b of the recess 2 a is constituted by the pair oflead electrodes 21 and the resin-molded body 22; and side surfaces ofthe recess 2 a are constituted by sidewalls 22 a of the resin-moldedbody 22. One pair of the sidewalls 22 a located opposite in the Z-axisdirection and constituting upper and lower side surfaces of the recess 2a have a smaller thickness than the other pair of the sidewalls 22 alocated opposite in the X-direction and constituting lateral sidesurfaces of the recess 2 a.

The light-emitting element 3 is arranged in the recess 2 a. Thesidewalls 22 a are formed such as to surround the light-emitting element3. The sidewalls 22 a are formed to have inner surfaces inclined at apredetermined angle relative to the bottom surface 2 b such that therecess 2 a expands from the bottom surface 2 b to the opening of therecess 2 a. With this structure, light emitted from the light-emittingelement 3 in lateral directions thereof is reflected by the sidewalls 22a toward the opening and extracted from the package 2.

The resin-molded body 22 comprises the resin composition 20 having goodlight-reflecting properties so that the light from the light-emittingelement 3 is reflected by the resin-molded body 22 and efficientlyextracted from the opening of the recess 2 a.

Recently, packages have been made thinner and thinner in response to anincreasing demand for smaller light-emitting devices. For this reason,specifically, it is desirable that the resin-molded body 22 surroundingthe light-emitting element 3 has a portion having a thickness of 100 μmor less, or more desirably a thickness of 50 μm or less.

In the package 2 according to the present embodiment, the opening of therecess 2 a is of an oval shape. The package 2 can be formed to have asmall outer dimension in the thickness direction without changing thedimensions of the recess 2 a, by forming the pair of sidewalls 22 aextending in the lengthwise direction of the opening of the recess 2 ato have a small thickness. This structure enables making thelight-emitting device 1 thin.

The sidewalls 22 a can have necessary mechanical strength even whenformed to have a small thickness, by being formed of the resincomposition 20 containing the fibrous first filling material 202. Thesidewalls 22 a exhibits necessary light reflectivity even when formed tohave a small thickness, because the coating material 202 b for enhancinglight reflectivity is provided in the first filling material 202.

Although the opening of the recess 2 a of the package 2 in the presentembodiment is of an oval shape, the shape of the opening may be acircular shape, an elliptical shape, or other polygonal shape.

Lead Electrode

The lead electrodes 21 are wiring lines for connecting an external powersource and the light-emitting element 3. The pair of lead electrodes 21of the package 2 in the present embodiment correspond to an anode and acathode of the light-emitting element 3. When a plurality oflight-emitting elements 3 are to be mounted, three or more leadelectrodes 21 may be provided according to the electrical connectionmanner of the light-emitting elements 3.

The pair of lead electrodes 21 is formed in the bottom surface 2 b ofthe recess 2 a such as to be exposed from the resin-molded body 22. Thepair of lead electrodes 21 is arranged such as to occupy a half or moreof the area of the bottom surface 2 b of the recess 2 a. Thelight-emitting element 3 is connected with the pair of lead electrodes21 at portions thereof exposed on the bottom surface 2 b, viaelectrically conductive members such as wires and solder. In the presentembodiment, the light-emitting element 3 is bonded to the pair of leadelectrodes 21 at the portions thereof exposed on the bottom surface 2 b.

Each of the pair of lead electrodes 21 has an outer portion projectingout of the resin-molded body 22 and bent to be arranged on a lowersurface of the package 2, i.e., the mounting surface. The light-emittingdevice 1 is bonded to an external circuit board or the like via theouter portions of the pair of lead electrodes 21 arranged on the lowersurface of the package 2.

The lead electrodes 21 may have any shape depending on the shape of thepackage 2. For example, the lead electrodes 21 may have a plate-likeform, a block-like form, or a film-like form, and may have a wavysurface or an uneven surface. The lead electrodes 21 may each have auniform thickness, or may each partially have a thick portion and/or athin portion. Although not particularly limited, the lead electrodes 21preferably have a wide width for the purpose of improving heatdissipation. Although not particularly limited, the material of the leadelectrodes 21 preferably has comparatively high electrical conductivityand comparatively high thermal conductivity. The lead electrodes 21 madeof such a material allows for efficient dissipation of the heatgenerated by the light-emitting element 3 to the outside. For example,preferably, the material for the lead electrodes 21 is a material havinga large thermal conductivity of about 200 W/m·K or more, a materialhaving a comparatively large mechanical strength, or a material easy topunch or etch. Specific examples of the material for the lead electrodes21 include: metals such as copper, aluminum, gold, silver, tungsten,iron, and nickel; and alloys such as iron-nickel alloys and phosphorbronze. Preferably, the lead electrodes 21 have surfaces plated with ametal having good light-reflecting properties, such as silver andaluminum, to efficiently extract light from the light-emitting element 3mounted on the lead electrodes 21. Preferably, the plated surface has aglossiness of 0.2 to 2.0, from the viewpoint of light extractionefficiency and manufacturing cost.

Resin-Molded Body

The resin-molded body 22 is formed to provide the recess 2 a, thepurpose of which is to hold the lead electrodes 21 and mount thelight-emitting element 3 together with the lead electrodes 21. In theresin-molded body 22, at least the sidewalls 22 a constituting the sidesurfaces of the recess 2 a comprises the resin composition 20 havinggood mechanical strength and light reflectivity.

The resin-molded body 22 may be formed by a known resin molding method,such as transfer molding, injection molding, compression molding, andextrusion molding.

Resin Composition

The resin composition 20 includes the light-transmissive resin 201containing the first filling material 202 for improving mechanicalstrength and light reflectivity. The resin composition 20 in the presentembodiment may include the second filling material 203 for furtherimproving light reflectivity.

The resin composition 20 may include additional materials conventionallyused for synthetic resins in addition to the first filling material 202and the second filling material 203, so long as the preferredcharacteristics of those filling materials are not impaired. Examples ofsuch additional materials include: inorganic filling materials such astalc, silica, and zinc oxide; flame retardants; plasticizers; diffusingagents; dyes; pigments; releasants; ultraviolet absorbers; antioxidants;thermostabilizers; and combinations of the foregoing. Herein, thepigments include white pigments.

Resin

Preferably, the resin 201 contains a resin material having goodlight-transmissive properties. Examples of such a resin material includethermoplastic resins, such as liquid crystal polymers, polyamide resins,polyphthalamide resins, and polybutylene terephthalates. Alternatively,the resin 201 may be a thermosetting resin, examples of which includeepoxy resins and silicone resins. Thermoplastic resins are veryinexpensive compared to ceramics, and thus are useful in providinglow-cost light-emitting devices. Thermosetting resins have better heatresistance than thermoplastic resins, and thus are useful in providinglight-emitting devices having good heat resistance.

First Filling Material

The first filling material 202 is a granular filler to be contained inthe resin 201 to enhance the mechanical strength of the resin-moldedbody 22 using the resin composition 20. Preferably, the particles of thefirst filling material 202 are of an elongated shape, such as a fibrousshape, a needle-like shape, or a stick-like shape, from the viewpoint ofenhancing the mechanical strength of the resin-molded body 22. Inaddition, the particles of the first filling material preferably have acertain size. If the particles of the first filling material 202 are toolarge, the resin-molded body 22 may have a surface with unevenness,which causes insufficient adhesion to the sealing member 4, resulting ina separation between the resin-molded body 22 and the sealing member 4.Under the condition that the total volume of the first filling material202 in the resin-molded body 22 is the same, the smaller the volume ofeach individual particle of the first filling material 202, the largerthe total surface area of the first filling material 202. The larger thetotal surface area of the first filling material 202 in the resin-moldedbody 22, the greater the light reflectivity of the resin-molded body 22.

Taking the above into account, the average fiber diameter, i.e., minordiameter, of the particles of the first filling material 202 ispreferably from 0.1 μm to 30 μm, more preferably from 0.1 μm to 15 μm,or still more preferably from 2 μm to 7 μm; the average fiber length,i.e., major diameter, of the particles of the first filling material 202is preferably from 1 μm to 100 μm, more preferably from 3 μm to 100 μm,or still more preferably from 20 μm to 50 μm; and the average aspectratio, i.e., ratio of major diameter to minor diameter, of the particlesof the first filling material 202 is preferably 3 or more, morepreferably from 3 to 50, or still more preferably from 5 to 30.

The content of the first filling material 202 in the resin composition20 is preferably from 5 to 70 percent by mass, or more preferably from10 to 70 percent by mass. The inclusion of the first filling material202 within these content ranges may enable the resin-molded body 22 tosatisfy high levels of requirements in terms of obtaining mechanicalproperties and optical properties required of the package 2 of thelight-emitting device 1.

Note that the first filling material 202 may contain two or more kindsof materials whose particles have different shapes.

Preferably, the elongated-shaped particles of the first filling material202 are randomly oriented in the resin-molded body 22, which may makethe mechanical strength of the resin-molded body 22 close to isotropic.Further, making both the resin-molded body 22 and the sealing member 4have isotropic mechanical strength makes them have the same behavior interms of their expansions and contractions due to temperature changes,which may inhibit the occurrence of a separation between theresin-molded body 22 and the sealing member 4 at an interfacetherebetween.

Meanwhile, the elongated-shaped particles of the first filling material202 may be arranged in the resin-molded body 22 so as to be oriented ina predetermined direction. Because the resin composition 20 is filledinto a mold with a predetermined pressure when molding the resin-moldedbody 22, the particles of the first filling material 202 may be orientedin the same direction, which makes the formed resin-molded body 22 havean anisotropic mechanical strength. This may enhance the mechanicalstrength of the resin-molded body 22 in a predetermined direction.

Base Material and Coating Material

To enhance the light reflectivity of the resin composition 20, in thefirst filling material 202, the surface of the base material 202 a iscoated with the coating material 202 b having good light-transmissiveproperties. Preferably, the coating material 202 b has betterlight-transmissivity than the base material 202 a. More preferably, thebase material 202 a has a refractive index higher than that of the resin201, and the coating material 202 b has a refractive index lower thanthat of the resin 201. Such a configuration makes the resin composition20 have a higher light reflectance compared to a case in which the firstfilling material 202 is solely composed of a base material 202 a notcoated with the coating material 202 b.

The coating material 202 b may be disposed such as to coat at least aportion of the surface of each particle of the base material 202 a. Itis, however, preferable that the coating material 202 b be disposed suchas to coat the entire surface of each particle of the base material 202a to enhance the light reflectivity of the resin composition 20.

Wollastonite, a kind of calcium silicate, can be used as the firstfilling material 202 to enhance the mechanical strength. As describedabove, wollastonite generally contains iron as an unavoidable impurity.When iron is mixed into the wollastonite as an impurity, the iron islikely to absorb light from the light-emitting element 3 and lightobtained by converting the wavelength of the light from thelight-emitting element 3 by phosphors or the like. An interface betweena filler and the resin 201 reflects light according to the differencebetween the refractive indices of the filler and the resin 201. Aportion of the light incident on the interface propagates into thefiller and is absorbed by the iron impurity. For this reason, use of aresin composition 20 containing a filler including wollastonite mayresult in poor light reflectivity.

For example, it is preferable that the base material 202 a have arefractive index of from 1.60 to 1.80, the resin 201 have a refractiveindex of from 1.48 to 1.59, and the coating material 202 b have arefractive index of from 1.35 to 1.47. Use of materials satisfying theseconditions may enhance light reflectivity.

A description is given of an example in which: wollastonite (refractiveindex: 1.63) is used as the base material 202 a; calcium fluoride(refractive index: 1.43) is used as the coating material 202 b; andpolyamide resin (refractive index: 1.50) is used as the resin 201.

In a comparative example of resin composition in which a fillercontaining the wollastonite but not containing the coating material 202b is used, the difference in the refractive index between the filler andthe resin 201 is 0.13, and the refractive index of the filler is greaterthan that of the resin 201. Accordingly, the light propagating in theresin 20 is reflected at an interface between the filler and the resin201 with a reflectance according to the difference in the refractiveindex.

In the example in which the filler of the wollastonite coated with thecoating material 202 b of calcium fluoride is used, the resin 201 andthe coating material 202 b have an interface therebetween having adifference of 0.07 in the refractive index, and the coating material 202b and the base material 202 a have an interface therebetween having adifference of 0.20 in the refractive index. Namely, the example has aninterface between the coating material 202 b and the base material 202 awhose difference in the refractive index is greater than that of theinterface between the filler and the resin 201 in the resin compositionof the comparative example. In addition, the example also has aninterface between the resin 201 and the coating material 202 b. Thoseinterfaces efficiently reflect light, resulting in reduction in theamount of light that propagates into the base material 202 a and isabsorbed therein. Therefore, the configuration of the example mayimprove light reflectivity of the resin composition 20.

Note that, because the coating material 202 b has a lower refractiveindex than the resin 201, total reflection according to the Snell's lawdoes not occur in the light incident from the coating material 202 b tothe interface between the coating material 202 b and the resin 201. Thatmeans the light propagating in the coating material 202 b is transmittedto the resin 201 in a comparatively efficient manner, which may enhancethe light reflectivity of the resin composition 20.

As the material for the base material 202 a, a first inorganic compoundcontaining a Group II element may be used. Preferably, the Group IIelement is Ca or Mg. Specifically, examples of the first inorganiccompound include calcium silicate and magnesium silicate. In particular,a wollastonite composed of calcium metasilicate, which is a kind ofcalcium silicate, can be easily processed into fibrous particles bycrushing, and thus is preferred as the base material 202 a of the firstfilling material 202 in terms of enhancing the mechanical strength ofthe resin composition 20.

As the material for the coating material 202 b, a second inorganiccompound containing the Group II element contained in the chemicalcomposition of the first inorganic compound, which is used for the basematerial 202 a, may be used. Preferably, the second inorganic compoundhas a smaller refractive index than the first inorganic compound and theresin 201 used in the resin composition 20.

Specifically, the second inorganic compound is preferably selected fromthe group consisting of a fluoride, a phosphate, and a sulfate whichincludes the Group II element. For example, when the Group II element isCa, examples of the second inorganic compound include calcium fluoride(CaF₂), calcium hydrogen phosphate (CaHPO₄), and calcium sulfate(CaSO₄). When the Group II element is Mg, examples of the secondinorganic compound include magnesium fluoride (MgF₂), magnesium hydrogenphosphate (MgHPO₄), and magnesium sulfate (MgSO₄).

To further improve the mechanical strength or the like of theresin-molded body 22, the first filling material 202 may be subjected toa known surface treatment using a silane coupling agent or a titaniumcoupling agent. As the agent for use in the surface treatment, a silanecoupling agent, in particular, amino silane is preferred. Surfacetreatment with a silane coupling agent or the like improves adhesionbetween the first filling material 202 and the resin 201, and thusenhances the mechanical strength of the resin-molded body 22. Inaddition, the surface treatment improves sliding properties of thesurface of the first filling material 202, and thus improves fluidity ofthe resin composition 20 before being cured. Due to the improvedfluidity, when molding the resin composition 20, the resin composition20 before being cured can be distributed throughout a mold cavity.

Second Filling Material

The second filling material 203 is a filler that is added to the resincomposition 20 when the resin composition 20 is required to have a lightreflectivity higher than that imparted by the first filling material202. The second filling material 203 may be arranged in the resin-moldedbody 22 molded using the resin composition 20 so that the second fillingmaterial 203 may be uniformly dispersed in the resin-molded body 22 orunevenly distributed and concentrated at or near an surface of theresin-molded body 22. Preferably, the second filling material 203 hasinsulation properties. The second filling material 203 having insulationproperties prevents the pair of lead electrodes 21 from being shortedvia the second filling material 203. Thus, the second filling material203 can be contained in the resin-molded body 22 at a comparatively highcontent.

Preferably, the material for the second filling material 203 has arefractive index largely different from that of the resin 201 used inthe resin composition 20. For example, particles of titanium oxide(TiO₂) or aluminum oxide (Al₂O₃) may be used for the second fillingmaterial 203. The diameter of the particles of the second fillingmaterial 203 is preferably in a range of 0.08 μm to 10 μm, or morepreferably in a range of 0.1 μm to 5 μm, so as to obtainlight-scattering effects at high efficiency. The content of the secondfilling material 203 in the resin composition 20 is preferably 10percent by mass to 60 percent by mass, or more preferably 20 percent bymass to 50 percent by mass, so as to enhance light reflectivity within arange where the formability of the resin composition 20 is not impaired.

Light Emitting Element

The light-emitting element 3 may be made by forming a semiconductor suchas GaAlN, ZnS, ZnSe, SiC, GaP, GaAlAs, AlN, InN, AlInGaP, InGaN, GaN, orAlInGaN on a sapphire substrate or the like as a light-emitting layer.Of these, a nitride-based compound semiconductor element having a peakemission wavelength in a short wavelength range from a ultravioletregion to a visible light region (360 nm to 550 nm) may be used. Evenwhen a light-emitting element 3 having high light emission output isused, because the resin-molded body 22 has high light reflectivity bycontaining the first filling material 202 in which the surface of thebase material 202 a is coated by the coating material 202 b, the lightfrom the light-emitting element 3 may not be able to penetrate into theresin-molded body 22. Accordingly, it may be possible to inhibitdegradation of the resin-molded body 22 due to light, and thus improvethe light resistance of the package 2.

Incidentally, it may also be possible to use a light-emitting elementhaving a peak emission wavelength in a long wavelength range of visiblelight (551 nm to 780 nm).

A plurality of the light-emitting elements 3 may be used. Usinglight-emitting elements 3 having different emission colors allows forproviding a light-emitting device 1 having a wide color reproductionrange. For example, two light-emitting elements 3 capable of emittinggreen light, one light-emitting element 3 capable of emitting bluelight, and one light-emitting element 3 capable of emitting red lightmay be used.

To use the light-emitting device 1 for pixels of a full-color displaydevice, it is preferable that the emission wavelength of the redlight-emitting element 3 be from 610 nm to 700 nm, the emissionwavelength of the green light-emitting elements 3 be from 495 nm to 565nm, and the emission wavelength of the blue light-emitting element 3 befrom 430 nm to 490 nm. When the light-emitting device 1 is configured toemit white mixed-color light, taking into account the complementaryrelation in the emission wavelength between the color of thelight-emitting element 3 and the color of the fluorescent substancecontained in the sealing member 4, and the deterioration of the sealingmember 4 caused by the optical output of the light-emitting element 3,the emission wavelength of the light-emitting elements 3 is preferably400 nm or more and 530 nm or less, or more preferably 420 nm or more and490 nm or less.

Sealing Member

The sealing member 4 is disposed in the recess 2 a of the package 2 toseal the light-emitting element 3, the lead electrodes 21, and wiresconnecting the light-emitting element 3 and the lead electrodes 21,which are arranged in the recess 2 a. Optionally, the sealing member 4may be omitted. However, the sealing member 4 serves to protect thesealed members from degradation due to moisture and gases, and damagesdue to physical contacts.

The material usable for the sealing member 4 is not limited. However, itis preferable that the sealing member 4 has good light-transmissiveproperties. Examples of such a material include: resin material such assilicone resins and epoxy resins, and inorganic materials such as glass.

The sealing member 4 may contain: fluorescent substance that performswavelength conversion on the light from the light-emitting element 3,and light-reflecting substance that scatters the light from thelight-emitting element 3. As the light-reflecting substance, the samematerials as the above-described materials for the second fillingmaterial 203 may be used.

As the fluorescent substance, one that absorbs the light from thelight-emitting element 3 and converts the absorbed light to light havinga wavelength different from that of the absorbed light may be used. Forexample, it is preferable to employ a material selected from the groupconsisting of: aluminum-garnet based phosphors; nitride-based phosphors,oxynitride-based phosphors, and sialon-based phosphors which areactivated mainly with a lanthanoid element such as Eu or Ce;alkaline-earth halogen apatite phosphors, alkaline-earth metal boricacid halogen phosphors, alkaline-earth metal aluminate phosphors,alkaline-earth silicate, alkaline-earth sulfide, alkaline-earththiogallates, alkaline-earth silicon nitrides, and germanates which areactivated mainly with a lanthanoid element such as Eu and/or atransition-metal element such as Mn; rare-earth aluminates andrare-earth silicates which are activated mainly with a lanthanoidelement such as Ce; organic compounds and organic complexes which areactivated mainly with a lanthanoid element such as Eu; and mixturesthereof.

Method of Manufacturing Light-Emitting Device

Next, a description is given of a method of manufacturing the fillingmaterials, resin composition, package, and light-emitting device withreference to FIGS. 1 to 4D. FIG. 3 is a flowchart illustrating the flowof a method of manufacturing the light-emitting device according to theembodiment. FIG. 4A is a schematic cross-sectional view illustrating aparticle of a first inorganic compound, which is the material for thefirst filling material in the method of manufacturing the light-emittingdevice according to the embodiment. FIG. 4B is a schematiccross-sectional view illustrating the particle of the first fillingmaterial which has been subjected to a surface treatment step in themethod of manufacturing the light-emitting device according to theembodiment. FIG. 4C is a schematic cross-sectional view illustrating anexample of the particle of the first filling material which has beensubjected to a heat treatment step in the method of manufacturing thelight-emitting device according to the embodiment. FIG. 4D is aschematic cross-sectional view illustrating another example of aparticle of the first filling material which has been subjected to theheat treatment step in the method of manufacturing the light-emittingdevice according to the embodiment.

Note that the example of the particle of the first filling materialshown in FIG. 4C indicates that the surface of the base material isentirely coated by coating material, and the another example of theparticle of the first filling material shown in FIG. 4D indicates thatthe surface of the base material is partially coated by coatingmaterial.

The method of manufacturing a light-emitting device according to thepresent embodiment includes: a filling material preparation step S10, amixing step S21, a resin-molded body forming step S31, a light-emittingelement mounting step S40, and a sealing member forming step S50. Thefilling material preparation step S10 includes: a surface treatment step(first step) S11 and a heat treatment step (second step) S12.

The filling material preparation step S10 and the mixing step S21 areincluded in a resin composition preparation step S20. The resincomposition preparation step S20 and the resin-molded body forming stepS31 are included in a package preparation step S30.

Hereinafter, a detailed description is given of each step.

Filling Material Preparation Step

The filling material preparation step S10 is a step for preparing thefirst filling material 202, and includes the surface treatment step(first step) S11 and the heat treatment step (second step) S12.

Surface Treatment Step (First Step)

The surface treatment step S11 performs a chemical surface treatment ona granular base material 202 a comprising a first inorganic compound inorder to form particles comprising a second inorganic compound throughself-assembly thereof on the surface the base material 202 a. Theparticles of the second inorganic compound become the coating material202 b.

As an example, a description is given of a case in which fibrousparticles of wollastonite (CaSiO₃) are used as the base material 202 acomprising the first inorganic compound and calcium fluoride (CaF₂) isused as the second inorganic compound. In this case, an aqueous solutionof ammonium fluoride is used as an agent to synthesize calcium fluoride,i.e., the second inorganic compound, from wollastonite, i.e., the firstinorganic compound.

Dispersing particles of the wollastonite in the aqueous solution ofammonium fluoride produces calcium fluoride on the surface of theparticles of the wollastonite, through the chemical reaction representedby the following formula:CaSiO₃+2NH₄F→CaF₂+SiO₂+2NH₃+H₂O

The produced calcium fluoride self-assembles into particles thereof onthe surfaces of the particles of the wollastonite. The particles of thecalcium fluoride serve as the coating material 202 b.

Note that, because the particles of calcium fluoride, i.e., coatingmaterial 202 b, are formed on the surface of the wollastonite, i.e.,base material 202 a, through self-assembly, the particles of the coatingmaterial 202 b and the base material 202 a are continuously formedwithout defining a clear interface therebetween.

Specifically, fibrous wollastonite, i.e., the base material 202 a, isadded into the aqueous solution of ammonium fluoride, and then theaqueous solution is stirred to form a suspension therein in which thewollastonite is uniformly dispersed. Preferably, the stirring isperformed gently so as not to destroy the shape of the wollastonite.While stirring the suspension, reaction is made in a predeterminedperiod of time at a predetermined temperature so as to produce particlesof calcium fluoride on the surfaces of wollastonite particles, i.e., thebase material 202 a.

Preferably, the particles of the coating material 202 b produced in thesurface treatment step S11 are nanoscale particles having a particlediameter (mode diameter) of 5 nm to 700 nm, or more preferably 5 nm to500 nm. Nanoscale particles of a substance are known to have a meltingpoint lower than that of the substance in a bulk state (for example,when the particle size is of the order of several micrometers or more),according to the size of the particles. Accordingly, the coatingmaterial 202 b being nanoscale particles allows itself to melt at alower temperature in the next heat treatment step S12.

Note that the above-mentioned diameter of the particles of the coatingmaterial 202 b can be measured using a photograph taken with a scanningelectron microscope (SEM).

The diameter of the particles of the coating material 202 b produced inthe surface treatment step S11 can be controlled by the conditions ofthe above-mentioned reaction, such as temperature, duration,concentration of agent, and pH. The conditions of the reaction aredetermined so that the dimensions of the particles of the base material202 a are controlled within a range such that the particles of the basematerial 202 a may serve as a filler for enhancing the mechanicalstrength of the resin composition 20.

The first filling material 202, in which the particles of the coatingmaterial 202 b have been formed on the surface of the base material 202a by the chemical surface treatment, may be subjected to dehydration,drying, and dry sieving steps, and then processed in the heat treatmentstep S12.

Heat Treatment Step (Second Step)

The heat treatment step S12 heats the first filling material 202 whichhas been subjected to the chemical surface treatment in the surfacetreatment step S11, so as to make the particles of the coating material202 b melt, thereby expanding the surface area of the base material 202a coated by the coating material 202 b.

In this step, the first filling material 202 is heated to a temperatureat which the base material 202 a does not melt but the coating material202 b melts. For example, when the base material 202 a is wollastonite,its melting point is about 1500° C. When the coating material 202 b iscalcium fluoride, its melting point is 1418° C. Thus, when the size ofthe particles of coating material 202 b is of the order of severalmicrometers or more, controlling the heating temperature at atemperature greater than or equal to 1418° C. and less than 1500° C. cancause only the coating material 202 b to melt. In contrast, forming thecoating material 202 b in nanoscale particles enables the particles ofthe coating material 202 b to melt at a temperature lower than theinherent melting point of calcium fluoride, i.e., 1418° C., at atemperature of, for example, several hundreds of degrees Celsius to1200° C., or, further, several hundreds of degrees Celsius to 1000° C.Therefore, the heat treatment step S12 can be carried out with a lowerheating temperature and/or in a shorter duration. In general, even whenthe difference in the inherent melting points between the firstinorganic compound and the second inorganic compound is small, formingthe particles of the coating material 202 b sufficiently smaller thanparticles of the base material 202 a and in nanoscale dimensions extendsthe difference in the melting point between the base material 202 a andthe coating material 202 b. This facilitates selectively making only thecoating material 202 b melt. Also, this may enable use of a combinationof a first inorganic compound and a second inorganic compound inherentlyhaving a melting point higher than that of the first inorganic compound.

The coating material 202 b formed in the surface treatment step S11 isdiscretely formed on the surface of the base material 202 a byself-assembling. Making the particles of the coating material 202 b meltonce causes the coating material 202 b to extend in a melt state,resulting in an increase in the area of the surface of the base material202 a coated by the coating material 202 b. Making the particles of thecoating material 202 b melt once also makes the surface of the coatingmaterial 202 b smooth, for example, like a mirror, and thus improves thelight reflectivity of the surface of the coating material 202 b.

The coating material 202 b may be arranged such as to coat at least aportion of the surface of the base material 202 a. It is, however,preferable that the coating material 202 b be arranged such as to coatthe entire surface of the base material 202 a. This improves the lightreflectivity of the resin composition 20 containing the first fillingmaterial 202.

Note that the area of the surface of the base material 202 a coated bythe coating material 202 b can be made larger by increasing thetemperature and the duration of the heat treatment.

When, like wollastonite, the particles of the first inorganic compoundused as the base material 202 a contain impurities such as an ironcomponent, the heat treatment is preferably carried out in a reducingatmosphere or an inert gas atmosphere. When the heat treatment iscarried out in an oxidizing atmosphere such as the atmosphere, the ironcomponent is converted into an oxide that exhibits greater visual lightabsorption. This reduces the light reflectivity of the resin composition20 containing the first filling material 202.

Taking this into account, the heat treatment is preferably carried outin a reducing gas atmosphere or an inert gas atmosphere to reduceoxidation of the iron component, thereby inhibiting the reduction in thelight reflectivity of resin composition 20 containing the first fillingmaterial 202.

Examples of the reducing atmosphere include a reducing gas atmospheresuch as a hydrogen gas and a carbon monoxide gas. Examples of the inertgas atmosphere include an argon gas atmosphere.

Carrying out the above steps manufactures the first filling material202.

Resin Composition Preparation Step

The resin composition preparation step S20 prepares the resincomposition 20 containing the resin 201 and the first filling material202. The resin composition preparation step S20 includes the fillingmaterial preparation step S10 and the mixing step S21.

Mixing Step S21

The mixing step S21 produces the resin composition 20 by adding thefirst filling material 202 prepared in the filling material preparationstep S10 to the light-transmissive resin 201 and mixing them.

In the mixing step S21 of the present embodiment, the second fillingmaterial 203, which is for imparting light reflectivity, may be blendedinto the resin composition 20 in addition to the first filling material202. Optionally, the resin composition 20 may be mixed further with theabove-mentioned filling materials and additives. Preferably, the firstfilling material 202 and the second filling material 203 are uniformlydispersed so as to reduce unevenness in the light reflection of theresin-molded body 22 using the resin composition 20.

The mixing step S21 can be carried out by a known mixing device such asa twin screw extruder.

Package Preparation Step

The package preparation step S30 manufactures the package 2 includingthe resin-molded body 22. The package preparation step S30 includes theresin composition preparation step S20 and the resin-molded body formingstep S31.

Resin-Molded Body Forming Step

The resin-molded body forming step S31 forms the resin-molded body 22using the resin composition 20 prepared in the resin compositionpreparation step S20. As the resin forming method for forming theresin-molded body 22, a known resin forming method, such as transfermolding, injection molding, compression molding, and extrusion moldingcan be used. The resin forming method is selected as appropriateaccording to whether the resin 201 used for the resin composition 20 isa thermosetting resin or a thermoplastic resin and according to thestructure of the package 2.

For example, when the resin 201 is a thermoplastic resin and the package2 is structured such that the lead electrodes 21 are held by theresin-molded body 22, injection molding may be used. Specifically, theresin-molded body 22 can be formed by clamping lead electrodes 21between vertically-divided molding dies and injecting melted resincomposition 20 into the molding dies.

Reducing the pressure applied to the resin composition 20 in forming theresin may make the resin-molded body 22 have isotropic mechanicalstrength. The resin-molded body 22 having the isotropic mechanicalstrength may inhibit the occurrence of a separation between theresin-molded body 22 and the sealing member 4 at a bonding interfacetherebetween. Meanwhile, using particles having an elongated shape, suchas a fibrous shape, a needle-like shape, or a stick-like shape as thefirst filling material 202 and increasing the pressure applied informing the resin may make the resin-molded body 22 have anisotropicmechanical strength. The resin-molded body 22 having the anisotropicmechanical strength may enhance the mechanical strength of theresin-molded body 22 in a predetermined direction.

Light-Emitting Element Mounting Step

The light-emitting element mounting step S40 mounts a light-emittingelement 3 in the package 2 manufactured in the package preparation stepS30.

In the present embodiment, the light-emitting element 3 is bonded to abottom surface 2 b of the recess 2 a of the package 2 using adie-bonding member; and pad electrodes of the light-emitting element 3and the lead electrodes 21 are electrically connected using wiringmembers such as wires.

Sealing Member Forming Step

The sealing member forming step S50 seals the light-emitting element 3and the lead electrodes 21 arranged in the recess 2 a by forming thesealing member 4 in the recess 2 a of the package 2.

Carrying out the package preparation step S30, the light-emittingelement mounting step S40, and the sealing member forming step S50 asdescribed above manufactures the light-emitting device 1.

Variant Embodiment

The light-emitting device 1 is not limited to the side-view type. Thelight-emitting device 1 may be of the top-view type, in which the lightextraction direction is perpendicular to the mounting surface. Thelight-emitting device 1 may be of the chip scale package type or chipsize package (CSP) type, in which the package 2 does not have the recess2 a and the light-reflective resin-molded body 22 is provided such as tocover side surfaces of the light-emitting element 3. Furthermore, thelight-emitting device 1 may be of the chip on board (COB) type, in whichthe light-emitting element 3 is arranged on a plate-shaped board and thelight-reflective resin-molded body 22 is formed in a frame shape on theboard such as to surround the light-emitting element 3.

The form of the light-emitting device 1 is not limited to thosedescribed above so long as the resin-molded body 22 is arranged tosurround at least a portion of the light-emitting element 3 such thatthe resin-molded body 22 is used to reflect the light from thelight-emitting element 3.

EXAMPLES

Next, examples of light-emitting devices in each of which alight-emitting element is mounted on a package using a resin compositioncontaining a first filling material and comparative examples aredescribed with reference to FIGS. 5A to 11B.

FIG. 5A is a photograph of a first filling material before subjected tothe surface treatment step. FIG. 5B is a photograph enlarging a part ofthe first filling material shown in FIG. 5A. FIG. 6A is a photographshowing a first filling material that has been subjected to the surfacetreatment step. FIG. 6B is a photograph enlarging a part of the firstfilling material shown in FIG. 6A. FIG. 7A is a photograph showing afirst filling material that has been subjected to the heat treatmentstep at a temperature of 850° C. in an example. FIG. 7B is a photographenlarging a part of the first filling material shown in FIG. 7A. FIG. 8Ais a photograph showing a first filling material that has been subjectedto the heat treatment step at a temperature of 900° C. in an example.FIG. 8B is a photograph enlarging a part of the first filling materialshown in FIG. 8A. FIG. 9A is a photograph showing a first fillingmaterial that has been subjected to the heat treatment step at atemperature of 950° C. in an example. FIG. 9B is a photograph enlarginga part of the first filling material shown in FIG. 9A. FIG. 10A is aphotograph showing a first filling material that has been subjected tothe heat treatment step at a temperature of 970° C. in an example. FIG.10B is a photograph enlarging a part of the first filling material shownin FIG. 10A. FIG. 11A is a photograph showing a first filling materialthat has been subjected to the heat treatment step at a temperature of1000° C. in an example. FIG. 11B is a photograph enlarging a part of thefirst filling material shown in FIG. 11A.

In FIGS. 5A, 6A, 7A, 8A, 9A, 10A, and 11A, a reading of 10 divisions inthe scale corresponds to 50 μm. In FIGS. 5B, 6B, 7B, 8B, 9B, 10B, and11B, a reading of 10 divisions in the scale corresponds to 1 μm, andeach figure is a photograph enlarging the surface of one particle ofeach first filling material. In FIG. 6B, the oblong, rectangularcolumn-shaped object is a particle of wollastonite serving as basematerial; and the many small particles formed on the surface of theparticle of wollastonite are particles of calcium fluoride serving ascoating material.

Original Material of Resin composition

The following materials were used for the light-emitting devices of theexamples and comparative examples.

-   -   Base material of the first filling material: Wollastonite        (Manufactured by KINSEI MATEC CO., LTD.; product name: SH1800;        average fiber diameter: 3.5 μm; average fiber length: 28 μm)    -   Agent used in the chemical surface treatment of the first        filling material: Aqueous ammonium fluoride solution    -   Second filling material: Titanium oxide (manufactured by        ISHIHARA SANGYO KAISHA, LTD.; product name: CR-90-2; average        particle diameter: 0.45 μm)    -   Resin: Polyamide resin PA6T (manufactured by Mitsui Chemicals,        Inc.; product name: ARLEN (R) C2000)    -   Package: Side-view type (manufactured by NICHIA Corporation;        product name: NSSW304D)

Examples

Packages of the examples were produced by the following procedure:

Surface Treatment Step

A wollastonite, the base material of the first filling material, wasdispersed in a 10% aqueous ammonium fluoride solution with a mass ratioof 1:10. While gently stirring the aqueous ammonium fluoride solution soas not to break the wollastonite, reaction was carried out for threehours at a temperature of 70° C. After the reaction, steps ofdehydration, drying, and dry sieving were carried out to obtainwollastonite having a surface on which particles of calcium fluoridewere formed.

Heat Treatment Step

Next, at each of the predetermined temperatures 850° C., 900° C., 950°C., 970° C., and 1000° C., a heat treatment was carried out for twohours in a reducing atmosphere so as to obtain a first filling materialcontaining particles of wollastonite on the surface of which a coatingmaterial comprising particles of calcium fluoride is melted andextended.

Note that, prior to carrying out the heat treatment at eachpredetermined temperature, the ambient temperature was increased from aroom temperature to the predetermined temperature taking four hours.

Now, a description is given of the difference in the shape of thecoating material due to the difference in the heating temperature withreference to FIGS. 5A to 11B.

As shown in FIG. 5B, the first filling material before surface treatmentwas applied was solely composed of the base material and had a flatsurface.

As shown in FIG. 6B, the particles of the coating materialself-assembled in the surface treatment step had a diameter of about 30nm to about 50 nm.

As shown in FIG. 7B, when the heating temperature was 850° C., theparticles of the coating material self-assembled in the chemical surfacetreatment remained in a granular form. The area of the base materialcoated by each of the particles of the coating material was larger thanbefore the heat treatment was carried out. However, the base materialhad many regions where the base material was exposed between theparticles of the coating material. Note that the particles of thecoating material once melted to form a smooth surface.

As shown in FIG. 8B, when the heating temperature was 900° C., theparticles self-assembled in the chemical surface treatment stillremained in a granular form, but the area of the base material coated bythe particles of the coating material was larger than when the heatingtemperature was 850° C.

As shown in FIG. 9B, when the heating temperature was 950° C., theparticles self-assembled in the chemical surface treatment stillremained in a granular form, but substantially the entire surface of thebase material was coated by the coating material.

As shown in FIG. 10B, when the heating temperature was 970° C.,substantially the entire surface of the base material was coated by thecoating material. In this case, the particles of the coating materialself-assembled in the chemical surface treatment had almost nogranularity, but had some amount of unevenness on their surface.

As shown in FIG. 11B, when the heating temperature was 1000° C.,substantially the entire surface of the base material was coated by thecoating material. In this case, the coating material has a surface withno unevenness and is formed in a film having a substantially uniformthickness.

Comparison between the FIGS. 5A, 6A, 7A, 8A, 9A, 10A, and 11A showedthat the each of the first filling materials remained in a fibrous formeven after being subjected to the surface treatment and the heattreatment under any of the conditions tested. Therefore, any of thosefirst filling materials can be used as a filler for enhancing themechanical strength of the resin composition.

Mixing Step

Next, two kinds of filling materials, i.e., a first filling materialhaving a surface on which the coating material was coated and a secondfilling material composed of titanium oxide, were mixed with a polyamideresin in the following ratio to obtain a resin composition.

The mass ratio of the polyamide resin, the first filling material, andthe second filling material in the resin composition was: 45 (polyamideresin): 15 (first filling material): 40 (second filling material). Thepolyamide resin, the first filling material, and the second fillingmaterial were melted and kneaded at a temperature higher than themelting point of the polyamide resin, e.g., 320° C., so as to uniformlydisperse the first filling material and the second filling material inthe polyamide resin. The kneading operation was carried out to dispersethe first filling material and the second filling material into thepolyamide resin, so gently as not to break the wollastonite, i.e., thebase material of the first filling material. After the kneadingoperation, pellets of the resin composition were produced by extrusionmolding.

Resin Molded-Body Forming Step

Next, the pellets of the resin composition were melted at a temperatureof about 320° C. and injected into an injection molding mold in whichlead electrodes are placed, to form a resin-molded body. The injectionmolded resin-molded body was then cooled to be solidified, to produce apackage. This package has a recess having a bottom surface and sidewalls, wherein at least a portion of a lead frame is exposed on thebottom surface and the side walls are formed of the resin-molded body.

Comparative Example

A package of the comparative example was produced in the followingprocedure:

-   -   The same material as the original wollastonite material used as        the first filling material in the examples and the same material        as the titanium oxide used as the second filling material in the        examples were prepared.    -   The first filling material and the second filling material were        kneaded in polyamide resin so as to be dispersed therein, in the        same manner as the examples. The mass ratio between the        polyamide resin, the first filling material, and the second        filling material was 45 (polyamide resin):15 (first filling        material):40 (second filling material). Then, a package was        produced in the same manner as the resin-molded body forming        step of the examples, except the conditions described above.

Evaluation

Light emitting devices were produced by mounting the same light-emittingelement on the packages of one of the examples and the comparativeexample. An evaluation was carried out as to a total luminous flux ofthe light emitted from each of those light-emitting devices when thelight-emitting element of the light-emitting device is made emit light.For each of the example and the comparative example, the luminous fluxof each light-emitting device was measured by an integral total luminousflux measurement apparatus.

Note that the light-emitting device of the example was the one producedusing the first filling material subjected to the heat treatment stepfor two hours at a temperature of 1000° C.

The evaluation result showed that, if the total luminous flux of thelight-emitting device of the comparative example is taken as 100, thetotal luminous flux of the light-emitting device of the example was100.5. Namely, it was confirmed that using the first filling material ofthe example enabled improvement in the light emission output of thelight-emitting device.

The light-emitting device according to the present disclosure can beused for lighting devices, displays, backlights for liquid crystaldisplay devices of cellular phones, auxiliary light sources for movingpicture illumination, and other general light sources for consumer use.

What is claimed is:
 1. A light-emitting device comprising: a packagehaving a recess; and a light-emitting element mounted in the recess,wherein the package comprises a resin composition comprising: alight-transmissive resin; and a filling material, wherein the fillingmaterial is dispersed in the light-transmissive resin, the fillingmaterial comprising: a base material, wherein the base materialcomprises a first inorganic compound containing a Group II element, anda coating material coating a portion of a surface of a particle of thebase material, wherein the coating material comprises a second inorganiccompound containing the Group II element and is different from the firstinorganic compound, and wherein the first inorganic compound and thesecond inorganic compound are in direct contact, wherein the firstinorganic compound is calcium silicate or wollastonite, and wherein thesecond inorganic compound is selected from the group consisting of afluoride including calcium, a phosphate including calcium, and a sulfateincluding calcium.
 2. The light-emitting device of claim 1, wherein thebase material is a fibrous material having an average fiber diameter of0.1 m to 15 m, an average fiber length of 1 m to 100 m, and an averageaspect ratio of 3 or more.
 3. The light-emitting device of claim 1,wherein the coating material coats continuously the entire surface ofthe particle of the base material.
 4. The light-emitting device of claim1, wherein the coating material is formed of nanoscale particles havinga particle diameter (mode diameter) of 5 nm to 700 nm.
 5. Thelight-emitting device of claim 1, wherein the coating material has ahigher light-transmissivity than the base material.
 6. Thelight-emitting device of claim 4, wherein the nanoscale particles haveonce melted, so that a surface of the coating material is smooth.
 7. Thelight-emitting device of claim 1, wherein the second inorganic compoundis one selected from the group consisting of calcium fluoride andcalcium hydrogen phosphate.
 8. The light-emitting device of claim 1,wherein the filling material has been subjected to a surface treatmentwith a silane coupling agent or a titanium coupling agent.
 9. Thelight-emitting device of claim 1, wherein the light-transmissive resinhas a refractive index lower than a refractive index of the basematerial and higher than a refractive index of the coating material. 10.The light-emitting device of claim 1, wherein the base material has arefractive index of 1.60 to 1.80, the light-transmissive resin has arefractive index of 1.48 to 1.59, and the coating material has arefractive index of 1.35 to 1.47.
 11. The light-emitting device of claim10, wherein the filling material is a first filling material, andwherein the resin composition further comprises a second fillingmaterial comprising particles of titanium oxide or aluminum oxide. 12.The light-emitting device claim 10, wherein a content of the fillingmaterial in the resin composition is from 5 mass percent to 70 masspercent.